I just changed the bearing balls in my front hub with 3/16" Grade 10 bearing balls that I located. I noticed a remarkable improvement (in my mind, at least!) from the existing balls. Do you think that this is just because the old bearings were remarkably dirty or do the Grade 10 balls make that much difference? Is this over kill? (Grade 100 or even grade 25 are less expensive and more readily available!) Thanks for your input!

Thanks for the reply Nigel! I was afraid that might be the case. However, I was pretty sure that I had to replace the balls and not just clean them, as they showed indications of pitting. I had ridden 2200 kilometers through rain and shine and I guess the original balls got wet. Then I waited too long before cleaning out the bearings (over a year!) and that did not help.
I saw some G25 bearings for sale on EBay for around $6 for 100, plus shipping, of course. When I stumbled upon the G10's, they were only a few dollars more for 20. if you considered the shipping costs for the G25's.
The ones I used were stainless, 440-C (because of riding in rain!) and were through hardened to Rockwell 58 to 60. Guess I should have just bought the G25's and I would have a few years worth of spares!

Also make sure you use a water repelling grease - I use grease intended for boat trailer wheel bearings for all my grease applications on my bikes.

Please note that 440C is not especially corrosion resistant compared to other stainless steel alloys. 52100 balls are stronger/harder than 440C balls, and more resistant to fretting (pitting) because of their higher hardness.

I worked on bearing systems for hard disk drives earlier in my career.

(10-02-2013, 12:20 AM)nfmisso Wrote: 52100 balls are stronger/harder than 440C balls, and more resistant to fretting (pitting) because of their higher hardness.

Technical question for you...Is there a potential downside to putting higher hardness bearings in? My vague understanding was that the hub cups were made of the hardest material, then axle cones, then finally relatively "soft" bearings. The idea being that you want damage to go to the easiest to replace part first. So overly durable bearings would risk wearing the axle/hub surfaces faster or even cause them to fail before the balls go.

If you look at the stress in the cups, cones and balls; you will find that the cups have the lowest stress, and the balls the highest, with the cones in the middle, but closer to the cups than the balls. The stress is a function of the radius of curvature; larger radius of curvature -> lower stress.

Some people use ceramic cartridge bearings, the vast majority of those have hard steel inner and outer races, with even harder ceramic balls. The balls still fail first. I do not recommend ceramic bearings for bicycles, the main issue being that the thermal expansion coefficient is not the same as steel (or aluminum or carbon fiber), which results in the fit changing over temperature. If you are a pro and have a pro mechanic tweaking things every time you stop for a minute - things are okay. For those of us without a full time pro mechanic following us around all the time we are biking - stay with steel on steel.

As far as I know (and I'm happy to be corrected) there is a disadvantage of using harder balls.
Unless you mean something different by Hardness, it usually comes with a loss of spring.

Ball bearings generally fail by gradual flaking, chipping and "spalling" of the outer skin because they experience maximum shear stress just below the surface

In use the balls elastically deform when under load, which is why grade 25 (accurate to 1/40000") is quite fine enough tolerance, certainly below 10 is irrelevant as, even if your cups and cones were that accurate, the balls and races distort many times that under load.

I'm unclear whether "stronger/harder" means Stronger & Harder, or just means you are mistaking stronger for harder.
Does the 52100 alloy distort less, fail less when distorting, or just have greater resistance to surface wear ?
Less distortion will increase stress both on the ball and the race due to the smaller contact area.
Friction wear, at the speeds involved in Bicycles, will be largely non existent on any hardened steel ball, and will anyhow be self levelling.
Greater resistance to failures while distorting is what we want.

Just re-built 2 French bikes (1970 Gitane, 1980 Peugeot) One with New #25 Steel Ball Bearings, and one with #5 Ceramics... First Grease/Bearing service ever!

I can tell you that it doesn't matter what type of balls you put in, you WILL TELL a difference in Old 30 to 40+ year old Grease, with NEW Grease, Balls, and Cones.... BOTH Bikes roll so much better now than before!!! Night and day difference!

The short ride I took on each a month ago, I Was I able to tell a difference between Steel & Ceramic on the two bikes? NO! I could not tell a difference between the two! They both rode far better than before!

Cost? (Ceramics would have been completely free if I hadn't requested the wrong bearing size ! I paid approximately the same: ~ $14 for new bearings on each bike! (Ceramics were a 'gift').

BUT... The re-build of the bikes with New Waterproof Grease, New Bearings, (and New Cones on the Peugeot).... FAR Outweighed any perceived benefits of Ceramic vs. Ball Bearings!

But... The Direction Received Here on positioning of Seat, Handlebars, etc., probably is just as important, and will be confirmed in 4 months!.

(01-10-2015, 03:58 PM)nfmisso Wrote: Sam; your understanding of materials and contact stress is lacking. Please go get a degree in Mechanical Engineering with a focus on Materials and Contact Mechanics.

For any given family of alloys (example iron based alloys like steel); there is a direct relationship between hardness and strength. The harder the material, the stronger it is.

Nigel; you don't actually address any of my questions. Just telling me I'm wrong because you're better qualified than me isn't particularly helpful.
My point was that hardness and ability to elastically deform are not the same thing. Cast iron is hard, but very brittle. There are different types of strength, and bicycle bearings require tough rather than hard.
Sorry if I'm not using the correct scientific terms, but neither, as far as I can tell, are you.

And Yes JanJ the rebuild is the key to improving ride, I just want to increase the time between rebuilds. I don't really bother with all this, shaving nano-newtons off the resistance, as you may have noted from my comment about bearing grades.

As LBS explained, the Lower the number, the less amount of imperfection (out of round)... 25 better than 50, 10 than 25, 5 than 10. etc...

These numbers In the case of my Peugeot, are not everything, as I found one of my front wheel cones that were drilled off center, and a slightly bent axle. Lucky me, the hubs were not grooved.
You could imagine the expression on my face when I saw the cone viewed end on! !

P.S. If there is someone around, Please remove the "Senior Member" tag on my name.... I'm still a novice who is basically self taught, and I'm here for direction!

(01-11-2015, 01:19 PM)joseph wolf man Wrote: ok i hate to sound stupid but what is the difference of the bearings the grade 10 and all the others ones you have listed im completely confused

The Grades are just a measure of how accurately round and accurate they are in millionths of an inch, so a G25 bearing can be ±0.000025" out of spherical or variation in size of the "lot" of bearings.
grade25 also dictates that they will be within ±0.0001 of the nominal size.
This is why people say you should always use bearings from the same batch i.e. they will be within ± 0.000025" of each other rather than ±0.0001" if you use grade 25 from mixed batches.

Grade 10 are ±0.00001" sphericity and lot variation and are within ±0.00005 of nominal measurement

Sam; a proper response would be several hundred pages of detailed technical information that is way beyond the scope of this forum. You have given no information as regards to your educational and experience back ground, so I have no idea where to start. If you are really interested, start by reading some papers on Hertzian contact stress, and R.E. Chinn's paper: "Hardness, Bearings, and the Rockwells," published in : Advanced Materials & Processes, Vol 167 #10, October 2009, p 29-31.